Optical Device for Use with Scanned Beam Light Sources

ABSTRACT

Substrate-guided relays that employ light guiding substrates to relay images from sources to viewers in optical display systems. The substrate-guided relays are comprised of an input coupler, an intermediate substrate, and an output coupler. In some embodiments, the output coupler is formed in a separate substrate that is coupled to the intermediate substrate. The output coupler may be placed in front of or behind the intermediate substrate, and may employ two or more partially reflective surfaces to couple light from the coupler. In some embodiments, the input coupler is coupled to the intermediate substrate in a manner that the optical axis of the input coupler intersects the optical axis of the intermediate substrate at a non-perpendicular angle.

BACKGROUND

Head-mounted and other compact display systems, such as head-up displays(HUDs), laptops, monitors, and other systems often rely on opticaldevices that overlay images onto transparent optical elements. Forexample, systems may display images through transparent lenses in frontof a user's eyes to enable the user to view displayed images at the sametime as viewing objects in the environment. Some of these displaysystems may utilize substrate-guided relays having three primarycomponents: an input coupler, a transmission substrate, and an outputcoupler. Light beams or other electromagnetic waves enter the relay viathe input coupler and remain confined within the relay due to totalinternal reflection or applied coatings. The beams are guided to theoutput coupler within the substrate, and the beams exit the relay viathe output coupler.

Various techniques may be used to insert light into substrate-guidedrelays. Some current systems use diffractive collimation (where LCDpanels transmit light to a holographic element that inserts light into arelay) and/or refractive collimation (where lenses insert LCD producedlight into the relay). However, these systems require increases in sizein order to expand the field of view or exit pupil expansion. Displaysystems relying on these techniques are therefore large and heavy when awide field of view is desired.

Various techniques may be used to couple light out of substrate-guidedrelays. Some current relays employ transmission substrates that havemirrors embedded in the substrate to couple light from the substrate.Although relays relying on this structure may provide a desirable formfactor, the relays require numerous reflectors each having a differentand precise reflectance characteristic, which create discontinuities inan image within the relay and images seen through the relay. They oftendo not efficiently couple light out of the substrate.

A short-coming of existing substrate-guided relays is that they are notcompatible with recent advances in light source technology. For example,current substrate-guided relays are sub-optimal when used with scannedbeam light sources to create images, such as systems that use MEMS basedscanning mirrors to scan a beam across two axes to create an image.Scanned beam light sources produce narrower input beams and currentrelays have poor efficiency and do not generate sufficient duplicates toproduce a uniform image or pupil for smaller scanned beam based images.Additional problems arise when expanding the field of view or the pupilwith current relays, making the relays difficult to fabricate andmanufacture.

These and other problems exist with adapting current substrate-guidedrelays for scanned beam light sources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a top cross-sectional view illustrating a substrate-guidedrelay having an angled input coupler and separate output coupler.

FIG. 1B is a rear view illustrating a substrate-guided relay having anangled input coupler and separate output coupler.

FIG. 1C is an isometric view illustrating a substrate-guided relayhaving an angled input coupler and separate output coupler.

FIG. 1D is an isometric view illustrating the presence of light rayswithin the relay of FIG. 1C.

FIG. 1E is a top cross-sectional view illustrating the substrate-guidedrelay of FIG. 1A adapted for use in eyewear.

FIG. 2A is a top cross-sectional view of a combination outputcoupler/intermediate substrate.

FIG. 2B is a top cross-sectional view of a combination outputcoupler/intermediate substrate having a varying reflectance layer at aninterface of the combination.

FIGS. 2C and 2D are top and side cross-sectional views of a combinationoutput coupler and intermediate substrate with the output couplermounted on the opposite surface.

FIGS. 2E and 2F are side and top cross-sectional views of a combinationinput coupler and intermediate substrate with the input coupler mountedat a 45 degree angle with respect to the intermediate substrate.

FIGS. 2G and 2H are side and top cross-sectional views of a combinationinput coupler, intermediate substrate, output coupler and cross coupler.

FIG. 3A is a top cross-sectional view of a combination outputcoupler/intermediate substrate having an internal homogenization layer.

FIG. 3B is a top cross-sectional view of a combination outputcoupler/intermediate substrate having an external homogenization layer.

FIG. 3C is a top cross-sectional view of a combination outputcoupler/intermediate substrate having a discrete homogenizationcomponent.

FIG. 4A is a top cross-sectional view of a combination outputcoupler/intermediate substrate having a discrete homogenizationcomponent and a partially reflective layer.

FIG. 4B is a top cross-sectional view of an intermediate substrateincluding two homogenization layers.

FIG. 5A is a top cross-sectional view of an input coupler having anangled interface surface.

FIG. 5B is a top cross-sectional view of an input coupler proximate toan intermediate substrate.

FIG. 6A is a top cross-sectional view of an input coupler having anangled interface surface and an external homogenization layer.

FIG. 6B is a top cross-sectional view of an input coupler having anangled interface surface and an internal homogenization layer.

FIG. 7A is an exploded view of the relay in some embodiments.

FIG. 7B is an exploded view of the relay in some embodiments.

FIG. 8 is a top cross-sectional view of components for coupling lightinto a substrate-guided relay.

FIG. 9 depicts a cross-sectional view of reflectors used to couple lightinto a substrate-guided relay.

FIG. 10 depicts an isometric view of eyewear incorporating asubstrate-guided relay.

DETAILED DESCRIPTION

Various substrate-guided relays that employ light guiding substrates torelay images from sources to viewers in optical display systems aredisclosed. The substrate-guided relays are comprised of an inputcoupler, an intermediate substrate, and an output coupler. In someembodiments, the output coupler is formed in a separate substrate thatis coupled to the intermediate substrate. The output coupler may beplaced in front of or behind the intermediate substrate, and may employtwo or more partially reflective surfaces to couple light to and/or fromthe coupler. In some embodiments, the input coupler is coupled to theintermediate substrate in a manner that the optical axis of the inputcoupler intersects the optical axis of the intermediate substrate at anon-perpendicular angle. In some embodiments, the input coupler iscoupled to the intermediate substrate in a manner that the optical axisof the input coupler intersects the optical axis of the intermediatesubstrate at a perpendicular or substantially perpendicular angle.Relays having the disclosed construction may be optimized to provide alarge field of view for images formed from scanned beam light sources,such as lasers. Similarly, relays having the disclosed construction maybe optimized to provide a large field of view for images formed fromother light sources, such as non-scanned beam light sources. The relaysmay also be optimized based on pupil location of a viewer (e.g., thelocation of the pupil within a produced field of view), pupildimensions, pupil uniformity (e.g., providing a uniform image to theentire pupil), and may be modified to achieve desired image brightness,see through uniformity, see through brightness, and simplicity ofmanufacture.

The relay construction disclosed herein provides a compact form factorthat may be incorporated in thin, lightweight devices that produceimages over desired fields of view. The relays may be incorporated inhead-mounted and other compact displays, such as head-up displays(HUDs). For example, eyeglasses and other head-mounted optical devicesmay incorporate the relays described herein. These head-mounted devicesmay be transparent or non-transparent (e.g., colored or tinted),realizing similar benefits described herein. Other devices, such asmobile communication devices and other compact devices may also employthe relays.

Various example relays will now be described. The following descriptionprovides specific details for a thorough understanding and enablingdescription of these examples. One skilled in the art will understand,however, that the technology may be practiced without many of thesedetails. Additionally, some well-known structures or functions may notbe shown or described in detail, so as to avoid unnecessarily obscuringthe relevant description of the various examples.

The terminology used in the description presented below is intended tobe interpreted in its broadest reasonable manner, even though it isbeing used in conjunction with a detailed description of certainspecific examples of the technology. Certain terms may even beemphasized below; however, any terminology intended to be interpreted inany restricted manner will be overtly and specifically defined as suchin this Detailed Description section.

Substrate-Guided Relays

FIG. 1A is a top cross-sectional view illustrating a substrate-guidedrelay 100 having an angled input coupler 110 coupled to an intermediatesubstrate 120 and separate output coupler 130. The input coupler 110receives light from a light source (not shown), such as a laser or otherscanned beam source, an LCD, LED, DLP, and so on. For example, the lightmay be in the form of an angularly encoded image from a source of lightthat produces an image in angle space. The input coupler conveys lightto the intermediate substrate 120, which is a slab guide or otheroptical substrate capable of conveying light from the input coupler tothe output coupler. As will be described in additional detail herein,the input coupler 110 may contact the intermediate substrate 120 at anangle, and may homogenize received light before conveying the light tothe intermediate substrate. The intermediate substrate 120 conveys lightreceived from the input coupler 110 to the output coupler 130. Theintermediate substrate 120 may additionally homogenize any receivedlight, further creating additional rays of the received light The outputcoupler 130 receives light from the intermediate substrate and enables aviewer (not shown) to view the displayed image. In some cases, theoutput coupler couples light out via embedded partially reflectivecomponents 132, such as partially reflective mirrors. Further detailsregarding the output coupler 130 are described herein.

FIG. 1B is a rear view of the substrate guided relay 100 of FIG. 1A. Theoutput coupler 130 is coupled to the intermediate substrate 120 at arear surface of the intermediate substrate 120. The input coupler 110,coupled to the intermediate substrate 120 across the length of theintermediate substrate, may introduce light into the intermediatesubstrate that subsequently conveys light to the output coupler 130 andout of the relay 100 via partially reflective components 132 within theoutput coupler.

FIG. 1C is an isometric view illustrating a substrate-guided relayhaving an angled input coupler and separate output coupler. Light isinserted into the input coupler 110 via an input component 140, such asa MEMS scanning mirror, reflective plate, LCD or other component capableof conveying a collimated beam of light to the input coupler 110. Theinput coupler conveys the beam of light to the intermediate substrate120. In the intermediate substrate 120, which may be a slab guide, thelight is optionally homogenized before being coupled out of the relayvia output coupler 130. In FIG. 1B, the output coupler is located on theface of the intermediate substrate that is closer to the viewer,however, the output coupler may be located on the face of theintermediate substrate that is away from the viewer as shown in otherfigures. In embodiments where the output coupler is away from theviewer, the relay may contain reflecting components 132 set at differentangles or may contain fewer reflecting components 132 than in otherconfigurations described herein.

FIG. 1D is an isometric view illustrating the presence of light waveswithin the relay of FIG. 1C and the impact of a homogenizer in therelay. For purposes of illustration, the input component 140 is depictedas inserting a single beam of light 150 into the input coupler 110 ofthe relay 100. In this example, the input coupler homogenizes the light,creating additional light beams 152 from the single beam of light. Forexample, more than 100,000 beams may be created from a single beaminserted into the input coupler. The light beams travel to the outputcoupler 130 via the intermediate substrate 120 and are conveyed out ofthe output coupler 130 to a viewer. The input coupler 110, theintermediate substrate 120, or both, may homogenize light within therelay 100, creating additional beams from beams inserted into the relay.In some cases, the relay homogenizes the light in order to improve theuniformity of the illumination, to increase the output brightness of animage, to expand an output field of view, to increase exit pupilexpansion, and so on.

FIG. 1E is a top cross-sectional view illustrating the substrate-guidedrelay of FIG. 1A adapted for use in eyewear. For example, a light beam,such as a beam from one or more lasers 144 is scanned across two axesusing a MEMS scanning mirror 142 and inserted into the input coupler110. The light beam may come from a light source contained within orattached to, for example, a frame of a pair of glasses. The beam (or,subsequently, beams) travels through the input coupler 110, theintermediate substrate 120, and out of output coupler 130 to a viewer'seye 160, positioned proximate to the output coupler 130. For example,the output coupler 130 is integrated with or attached to a lens of theglasses.

For scanned beam light sources, very thin substrates may be used for theinput coupler 110, intermediate substrate 120, and/or output coupler130. For example, the intermediate substrate may have a thickness ofless than 4 millimeters, and the output coupler may have a thickness ofless than 2 millimeters. The substrates may be formed of optical gradefused silica, glass, plastic, or other suitable materials. Using thesubstrate configuration described herein therefore allows a compact formfactor to be realized for the substrate-guided relay.

In some embodiments, the relay 100 may be manufactured at variousthicknesses and with different materials. For example, the thicknessand/or material of a relay 100 may be varied to ease the fabrication ofthe relay, to achieve better image uniformity, to lower the weight orsize of the relay, to provide better protection to a user's eye, toprovide a higher image quality, to produce the relay at a lower cost,and so on. The thickness and/or material of the relay 100 may depend onangles of insertion, reflection, transmission, or output of light withrespect to the relay 100.

Confinement of light within the relay may be due to the total internalreflection (TIR). For example, TIR provides for a high transmission oflight (approximately 100%) at see-through angles (approximately 0 to 25degrees), and high reflection of light at higher angles (approximately45 to 80 degrees) of incidence. The relay may also incorporate partiallyreflective coatings outside of or within the relay to achieve a similarconfinement of light.

Output Coupler/intermediate Substrate

FIG. 2A is a top cross-sectional view of a combination intermediatesubstrate 120 and output coupler 120. The intermediate substrate 120 isconfigured to contain and convey light to the output coupler 130. Theintermediate substrate 120 has, for example, a front face 202, having aninner surface 203 and an outer surface 204, and a back face 205, havingan inner surface 207 and an outer surface 206. The intermediatesubstrate 120 also has an input face 221 and a distal face 222. All or aportion of the surfaces 203, 207 of the intermediate substrate may beconfigured to confine a beam of light within the intermediate substrateusing total internal reflection. All or a portion of the surfaces 203,207 may be configured to allow a beam of light to leave the intermediatesubstrate 120. For example, the intermediate substrate may contain aguide section 208 where both inner surfaces 203, 207 of the sectionreflect all beams of light that impose on the surfaces. The intermediatesubstrate may also contain a coupling section 209 where the front innersurface 203 reflects any imposed light beams and the back inner surface207 allows some or all light beams to pass through to the output coupler130, reflecting any light beams back to the front inner surface 203 thatdo not travel to the output coupler 130. In some cases, the back innersurface 207 of the coupling section 209 may be graded or may vary withrespect to reflectivity and/or transmissivity.

FIG. 2B depicts a top cross-sectional view of a combination outputcoupler/intermediate substrate having a varying reflectance layer at aninterface 210 between the intermediate substrate 120 and the outputcoupler 130. For example, the back inner surface of the intermediatesubstrate may have an area of higher reflectivity 212 (such as 60percent) and an area of lower reflectivity 214 (such as 40 percent). Thevaried reflectivity surface may have discrete sections, or maycontinually vary, such as incrementally varying from a high reflectivityat area 212 to a low reflectivity at area 214. Reflectivity may vary asa function of angle of incident light, polarization of incident light,wavelength of incident light, or any combination. If the reflectivity ofthe surface was not varied, the intensity of the light exiting theoutput coupler may be less at a point closer to the distal face of theintermediate substrate as compared with a point closer to the input faceof the intermediate substrate. Varying the reflectivity/transmissivityprovides for a substantially uniform transmission of light beams fromthe intermediate substrate 120 to the output coupler 130, among otherbenefits.

In addition, creating a surface of varying reflectance may allow lightof one angle to be reflected more than light at another angle, or allowlight of one angle to be transmitted more than light at another angle.In some cases, this enables a distal portion of an image to travel to adistal location, and a closer portion of an image to travel to a closerlocation, creating a clear and more uniform image, among other benefits.

The output coupler 130 is configured to receive light beams from thecoupling section 209 of the intermediate substrate 120 and output thereceived beams to a viewer proximate to the output coupler. For example,the output coupler may include one or more partially reflective surfaces132 that reflect light beams out of the relay 100. The surfaces 132 arepartially reflective in order to provide the light beams to a viewerwhile at the same time allowing the viewer to see through the coupler130. In some cases the partially reflective surfaces 132 may besubstantially parallel with respect to one another. In some cases thepartially reflecting surfaces 132 may have substantially similar partialreflection coatings creating a substantially uniform output couplertransmission so that ambient light passing through the output coupler issubstantially uniform. In some cases, the partially reflective surfaces132 may be spaced in such a way that ambient beams of light may passthrough the relay without impinging on any of the surfaces 132 (that is,a viewer looking through the relay may be less distracted by thesurfaces 132 as some light beams reflected off objects outside the relaytravel through the intermediate substrate and output coupler unimpeded).Additional details about the construction of suitable partiallyreflective surfaces may be found in application Ser. No. 11/603,964,entitled “Substrate-Guided Display with Improved Image Quality,” filedNov. 21, 2006 and incorporated by this reference in its entirety.

FIGS. 2C and 2D depict top and side cross-sectional views of acombination input coupler 110, intermediate substrate 120, and outputcoupler 130, where the output coupler 130 is mounted on the oppositesurface of the intermediate substrate as the input coupler 110. In thisexample, the configuration of the input coupler 110 with respect to areflective or partially reflective surface 125 in the intermediatesubstrate 120 causes light 140 to be coupled into the intermediatesubstrate 120 at approximately 45 degree angles with respect to thelength of the intermediate substrate 120.

FIGS. 2E and 2F depict side and top cross-sectional views of acombination input coupler 110, intermediate substrate 120, and outputcoupler 130, where the input coupler 110 is mounted at a 45 degree anglewith respect to the intermediate substrate. In some examples the inputcoupler 110 is mounted on the same surface of the intermediate substrate120 as the output coupler 130. In some examples the input coupler 110 ismounted on the opposite surface of the intermediate substrate 120 as theoutput coupler 130. In some examples the input coupler 110 is mounted toan end surface 125 of the intermediate substrate 120.

FIGS. 2G and 2H depict side and top cross-sectional views of acombination input coupler 110, intermediate substrate 120, outputcoupler 130, and cross coupler 170. The cross coupler 170 may beconfigured or situated so as to create additional rays of light fromlight that enters the coupler 170. In some examples, the cross coupler170 is mounted on a surface opposite the surface between the inputcoupler 110 and the intermediate substrate 120. In some examples thecross coupler 170 is mounted to other surfaces of the input coupler 170.In some examples the cross coupler 170 may be located between the inputcoupler 110 and the intermediate substrate 120, or may be located onother surfaces of the intermediate substrate 120.

The surface between the cross coupler 170 and the input coupler 110includes a partially reflective coating 172. The cross coupler 170includes full or partial reflectors 171 used to redirect light thatpasses through coating 172 into the cross coupler 170. In some examples,the reflectors 171 redirect the light into the input coupler 110 atdifferent angles than other light coupled into the input coupler 110.The cross coupler 170 may take on different shapes, such as saw toothshapes similar to those depicted in FIG. 7A and discussed herein. Insome embodiments, the reflective surfaces 171 and the coating 172 mayvary discretely or continuously based on angles of incident light,polarization of incident light, wavelength of incident light, orcombinations. In addition, surfaces between components of thecombination may vary discretely or continuously as a function of angleof incidence, polarization, wavelength, or combinations.

In some embodiments, the reflective surfaces 132 in the output couplermay be coated in order to provide some or all of the benefits describedherein. For example, varying the reflectance of the reflective surfaces132 may enable an image spread uniformly across the output coupler. Thevaried reflective surfaces 132 may, therefore, assist moving light tointended locations.

In some embodiments, the intermediate substrate 120 may contain ahomogenization structure, such as the various layers and componentsshown in FIGS. 3A-3C. FIG. 3A depicts a top cross-sectional view of acombination output coupler/intermediate substrate having an internalhomogenization layer 310. The layer 310 may be an interface betweensubstrates of differing indices of refraction, may be a beam splittingtype interface, or may be a partially reflective layer that reflectspart of a beam or beams and transmits part of a beam or beams. The layer310 causes a single impinging beam 311 to form multiple beams 312, 313.Beam 312 passes through layer 310 unaffected and reflects off the innersurface 203 of the intermediate substrate 120. Beam 313 reflects offlayer 310 and creates a second beam having a different path through theintermediate substrate. Thus, the layer enables the system to duplicateor multiply a single beam into multiple beams. The multiple beams maythen exit the relay through the output coupler at different locations,providing a homogenized pupil and field of view to a viewer.

In some embodiments, the homogenization layer may be placed adjacent tothe front face 202 of the intermediate substrate 120. FIG. 3B is a topcross-sectional view of a combination output coupler/intermediatesubstrate having an external homogenization layer 320. In order to placethe homogenization layer on the front face 202 of the intermediatesubstrate 120, the front inner surface 203 of the intermediate substratemay be modified to partially reflect incident light beams and partiallytransmit incident light beams. A front inner surface 322 of thehomogenization layer may be configured to total internally reflect anyincident light beams, effectively acting to contain all light within theintermediate substrate. In such a construction, a single light beam 323that impinges on the front inner surface 203 of the intermediatesubstrate is partially reflected back into the intermediate substrate toform one beam 325 and partially transmitted into the homogenizationlayer 320 to form a second beam 324. Additionally, every subsequent beamwithin the intermediate substrate that impinges on the interface betweenthe intermediate substrate 120 and the homogenization layer 320 formstwo beams. Thus, the homogenization layer enables the system to formmany additional beams from a single inserted beam.

In some embodiments, the homogenization component may be a discretecomponent mounted to the front face 202 of the intermediate substrate120. FIG. 3C is a top cross-sectional view of a combination outputcoupler/intermediate substrate having a discrete homogenizationcomponent 330. A single beam 331 that impinges on the front innersurface 203 of the intermediate substrate is partially reflected backinto the intermediate substrate to form one beam 333 and partiallytransmitted into the discrete homogenization component 330 to form asecond beam 332. The second beam may propagate at a position offset tothe first beam. Additionally, the homogenization component 330 may formmany additionally beams, all offset from one another. As with theexternal homogenization layer 320 described in FIG. 3B, light may enterthe homogenization component 330 via a partially reflective interface335 between the component 330 and the front face 202 of the intermediatesubstrate 120. Thus, the component 330 enables the system to homogenizea single beam into multiple beams. As described herein, the multiplebeams may then exit the relay through the output coupler, providing asaturated field of view to a viewer.

In some embodiments, the homogenization may occur due to reflectorsplaced perpendicular with respect to substrate surfaces. FIG. 4A depictsa top cross-sectional view of a combination output coupler/intermediatesubstrate having a discrete homogenization component 330 and a partiallyreflective component or layer 410 placed perpendicular to surfaces ofthe intermediate substrate. Light may enter the discrete homogenizer 330via a partially reflective surface 335, or may pass through the layer410 before entering the homogenization component 330, creating manyadditional beams of the entering light that are offset from one another.

In addition, the combination output coupler/intermediate substrate mayinclude more than one component or layers 410 to achieve a variety ofdifferent offset homogenization patterns of light. FIG. 4B depicts anintermediate substrate including two homogenization layers 410 used tocreate many additional beams from input light. For example, some lightmay enter the substrate and pass through the first partially reflectivelayer 411 and the second partially reflective layer 412, and some lightmay pass through the first reflective layer 411, be reflected by thesecond layer 412, be reflected back by the first reflective layer 411 atan angle offset from the original entered light, and then pass throughthe second reflective layer 412 and into the intermediate substrate.Thus, beams offset from one another may be realized by a combination ofreflective layers 410.

In addition to the homogenization layers and components describedherein, other configurations able to homogenize a beam of light are ofcourse possible. For example, the system may employ two or morehomogenization layers, such as stacked layers having differing indicesof refraction or having partially reflective coatings between thelayers. In some cases, the layers or components may be substantiallyparallel to one another and to the intermediate substrate. The layers orcomponents may be of substantially same thickness or may vary inthickness. In some cases, the layers or components may be of differentshapes than those illustrated in the figures.

Input Coupler

FIG. 5A depicts a top cross-sectional view of the input coupler 110having an angled interface surface. The input coupler may be formed ofoptical grade fused silica or other isotropic materials. The inputcoupler is coupled to an intermediate substrate in a configuration wherethe angle of interface between the input coupler and intermediatesubstrate is not perpendicular. However, in some cases, the angle ofinterface may be perpendicular, depending on the needs of a user.

FIG. 5B depicts a top cross-sectional view of the input coupler 110proximate to the intermediate substrate 120. The angle θ of interfacebetween the input coupler 110 and the intermediate substrate may be anyangle, such as 135 degrees. A surface 510 of the input coupler may bepartially reflective, allowing some light beams to enter theintermediate substrate and reflecting some light beams back into theinput coupler 110. The reflective surface 510 may vary across theinterface, being more reflective at the end closest to where lightenters the input coupler and less reflective at the other end.

In an analogous manner to the operation of the intermediate substrate120, the input coupler 110 may homogenize a single beam (or, multiplebeams) into additional beams using a homogenization layer or othercomponent. FIG. 6A is a top cross-sectional view of an input coupler 110having an angled interface surface and an external homogenization layer610. The external layer 610 causes multiple beams 622 to form from asingle beam 620 at an interface 611 between the input coupler 110 andthe homogenization layer 610. FIG. 6B is a top cross-sectional view ofan input coupler 110 having an angled interface surface and an internalhomogenization layer 630. The internal layer 630 causes multiple beams622 to form from a single beam 620. The layer 630 may be a partiallyreflective layer, partially allowing a beam to pass through to theintermediate substrate and partially reflecting the beam to form asecond beam in the input coupler. As described herein with respect tothe various disclosed examples, the relay may be formed in a variety ofconfigurations. FIGS. 7A and 7B reflect a few of these configurations.For example, FIG. 7A depicts an exploded view of a relay 700, includingan input coupler 110, an intermediate substrate 120, an output coupler130, and a homogenization component or layer 610. FIG. 7B depicts arelay 710 having an alternative configuration, although it also includesan input coupler 110, an intermediate substrate 120, and an outputcoupler 130. Of course, other configurations of relays, input couplers,intermediate substrates, and/or output couplers are possible.

Coupling Light Into a Substrate

FIG. 8 depicts a cross-sectional view of components 800 used to couplelight into a substrate-guided relay. Polarized light is emitted by asource 810, such as one or more scanned beams sources. A lens 820collimates the polarized light, and the collimated light passes througha polarizing beamsplitter 830, through a quarter-wave plate 840, andreflects off of a scanning MEMS mirror 850. Once reflected by the mirror850, the light passes through the quarter wave plate 840 and is nowreflected off the polarizing beamsplitter 830 due to the rotation inpolarization of the light. The reflected light enters an input coupler860 (such as input coupler 110) via an input surface 865. In thisexample, the polarizing beamsplitter 830 is set at an angle relative tothe input surface 865 of the input coupler 860 so that beams reflectedoff the polarizing beamsplitter 830 impinge multiple internal surfacesof the input coupler 860. The angle between the beamsplitter 830 and theinput surface 865 may be set so that a central beam 870 of the lightpasses through the input surface 865 at near-normal incidence.

The depicted configuration of components 800 enables light to be coupledinto compact relays. In some examples, distances between components arechosen to minimize the spreading of light from the light source, toselect angles of inserting light into the coupler, and so on. Inaddition, different components may be implemented to achieve similarcoupling of light. For example, a reflector (such as a PBS) may beembedded within the input coupler 860, such as on the inside surface ofthe input surface 865. Light may be scanned by a MEMS scanner andcoupled into the input coupler 860 through one of the other surfaces867, such as by placing a prism on the surface to enable light to enterthe coupler. The directly-coupled light is reflected off of the embeddedreflector and through the input coupler. In some examples, the inputsurface 865 may be expanded to allow for wider angle coupling. Forexample, surface 865 may be larger than a cross-sectional surface of theinput coupler 860 at other locations. The size and shape of theexpansion of the surface 865 may be dependent on the configuration ofcomponents 800, or may be dependent on distances between the components.

FIG. 9 depicts a cross-sectional view of reflectors 910, 920 used tocouple light into a substrate-guided relay. In this embodiment,reflectors 910, 920 (such as partial reflectors, full reflectors, orreflectors having certain polarization or wavelength reflectingcharacteristics) are placed on outer surfaces of an input coupler 110(or, any substrate), to confine light within an area containing anair-substrate boundary 930. There may be a reflector 910, 920 placed onone surface, on two surfaces, or on all surfaces of the input coupler110. The reflectors (and the area between them) receives light rays froma scanned beam source and guides the light rays into the input coupler110, preventing the spread of light between the source and the inputcoupler. Light may enter at an opening, or may enter through one of thereflectors 910, 920, depending on the design needs of an associatedsubstrate guided-relay. For example, in some cases it may be beneficialfor light to enter through one of the reflectors in order to achieve adesirable input angle of light into the input coupler 110.

Use of Substrate-Guided Relay in Eyewear

In some embodiments, the substrate-guided relay may be used witheyewear, such as eyewear with lenses that are clear, colored or tintedfor certain optical effects or for desired fashionable effects. FIG. 10depicts an isometric view of eyewear 1000. Eyewear 1000 includes lenses1010 and a frame 1020. Frame 1020 may include some or all parts of aprojection system that incorporates a substrate-guided relay 100. Thesystem may be incorporated, for example, in the temple 1030 of frame1020. For example, the temple 1030 may contain a projector that projectslight through a substrate-guided relay 100 that allows a wearer of theeyewear 1000 to view images via the lenses 1010. The source of theimages may also be within the frame 1020, may be attached to the frame1020, or may be located within other components associated with a wearerof the eyewear 1000. For example, eyewear may be wired or wirelesslyconnected to a mobile device attached to a wearer of the eyewear. Themobile device may contain the image source, and transmit the images to asubstrate-guided relay within the frame 1020 of the eyewear 1000 forpresentation of the images to the wearer. Thus, users are able to viewimages on the lenses of the eyewear with minimal increases in weight dueto the source of the images being remote to the eyewear.

CONCLUSION

As used herein, the terms “connected,” “coupled,” or any variantthereof, means any connection or coupling, either direct or indirect,between two or more elements. The above detailed description ofembodiments of the system is not intended to be exhaustive or to limitthe system to the precise form disclosed above. While specificembodiments of, and examples for, the system are described above forillustrative purposes, various equivalent modifications are possiblewithin the scope of the system, as those skilled in the relevant artwill recognize. Accordingly, the invention is not limited except as bythe appended claims.

1-31. (canceled)
 32. An optical device that relays an image from animage source to a viewer, comprising: an input coupler that receives abeam representing a portion of the image and transmits the beam to anintermediate substrate, wherein the input coupler is attached to theintermediate substrate so that an optical axis of the input couplerintersects an optical axis of the intermediate substrate at anon-perpendicular angle; and an output coupler that receives the beamfrom the intermediate substrate and outputs the beam to the viewer, theoutput coupler attached to and external from the intermediate substrate.33. The optical device of claim 32, wherein the input coupler receivesthe beam representing a portion of the image and creates multiple beamsfrom the received beam.
 34. The optical device of claim 32, furthercomprising: a partially reflective layer located between the inputcoupler and the intermediate substrate.
 35. The optical device of claim34, wherein the partially reflective layer comprises a first area havinga first reflectivity value and a second area having a secondreflectivity value.
 36. The optical device of claim 32, furthercomprising: a homogenization component that causes a number of lightbeams received by the output coupler to be greater than a number oflight beams received by the input coupler.
 37. The optical device ofclaim 36, wherein the homogenization component is located inside theinput coupler.
 38. The optical device of claim 36, wherein thehomogenization component is located outside and adjacent to the inputcoupler.
 39. The optical device of claim 36, wherein the homogenizationcomponent is located inside the intermediate substrate.
 40. The opticaldevice of claim 36, wherein the homogenization component is locatedoutside and adjacent to the intermediate substrate.
 41. The opticaldevice of claim 32, wherein the input coupler contains partiallyreflective surfaces that direct the transmitted beam to the intermediatesubstrate.
 42. The optical device of claim 41, wherein the reflectivityof the partially reflective surfaces is dependent on a wavelength of anincident beam.
 43. The optical device of claim 41, wherein thereflectivity of the partially reflective surfaces is dependent on apolarization of an incident beam.
 44. The optical device of claim 41,wherein the reflectivity of the partially reflective surfaces isdependent on an angle of incidence of an incident beam.
 45. The opticaldevice of claim 32, wherein the input coupler is physically attached tothe intermediate substrate at a surface parallel with the optical axis.46. The optical device of claim 32, wherein the input coupler isphysically attached to the intermediate substrate at a surfaceperpendicular with the optical axis.
 47. The optical device of claim 32,wherein the intermediate substrate contains one or more partiallyreflective surfaces situated substantially parallel in relation to outersurfaces of the intermediate substrate, wherein the one or morepartially reflective surfaces are configured to reflect incident beamsof light having a first angle of incidence and transmit incident beamsof light having a second angle of incidence.
 48. The optical device ofclaim 32, wherein the output coupler contains two or more partiallyreflective surfaces each having a similar partial reflection coatingconfigured to output the beam from the output coupler and allow ambientbeams of light to pass through the output coupler. 49-51. (canceled)